1. Field of the Invention
This invention relates to a receptacle type ground fault circuit interrupter (GFCI) device, and in particular, the type of GFCI device using an electromagnetic tripper.
2. Description of the Related Art
GFCI is widely used at present because it can prevent electrical shock to a user to a certain extent and effectively prevent damage to the equipment and fire accidents caused by a ground fault.
The existing receptacle type GFCI includes an input circuit, a leakage current detecting and amplifying circuit, a neutral ground fault detecting and amplifying circuit, a signal control circuit and an output circuit. The power signal goes to the signal control circuit via the input circuit and the rectifying circuit A; a leak detecting signal is produced in the leak fault detecting and amplifying circuit and then input to the signal control circuit; and a ground fault detecting signal is produced in the neutral ground fault detecting and amplifying circuit and then input to the signal control circuit. The signal control circuit outputs the signals, after processing them, to the output circuit.
The rectifying circuit of the input circuit consists of four rectifying diodes D1, D2, D3 and D4 and changes an alternating current into a direct current. The connections between D1 and D2 and between D3 and D4 are connected to the AC input and form the input end of the GFCI. The connection between D2 and D3 forms the load end of the DC power, which will be called “the cathode of the input circuit” thereafter, and the one between D1 and D4 “the anode of the input circuit”.
Under a normal working condition, electric current is output from both the receptacle outlet and the load terminal of the GFCI, and the GFCI is in the reset state.
The detecting coils in the leak fault and neutral ground fault detecting and amplifying circuits are used to detect the leak or ground fault signals and, once a leak or ground fault signal detected, will send it to the signal control circuit for processing. The IC in the signal control circuit will then check if the signal is potentially dangerous to people or is harmful to the equipments and, if so, quickly produces a signal to activate the one-way silicon controlled rectifier (SCR1), thus causing the transistor Q1 and the working coil J1 to stop. The elastic dynamic contacts K1, K2, K3 and K4 of the circuit interrupter break, and the circuit interrupter is thus put in the tripped state.
The existing GFCI can be connected to a load through the outlets on the faceplate and the load wiring screws. If such a GFCI is out of its proper working condition for an unknown reason, since its lack of self indicating capability for a fault existing in its system, users may keep using it when the power is turned on at the power input end, which may cause an electric shock.